Stephen Colbert has appeared on CBS' Late Show for the first time since it was announced he would be taking over from current host David Letterman.

Colbert said he was "thrilled" with his new role and told him he was "going to do whatever you have done".

Letterman, 67, urged against it, saying: "You don't want to do that."

Introducing his successor, Letterman, who has hosted the show since 1993 and is retiring next year, said the new host was "very talented" and "always entertaining".

The host quipped "you look right at home," and greeted Colbert warmly, claiming the network "could have just as easily hired another boob" like him.

Colbert, 49, made his mark satirising political conservatives on his Comedy Central weeknight cable show, The Colbert Report.

He has previously said he would drop his known persona of a dim-witted, big-egoed conservative pundit.

Details of how the format of the Late Show will change under Colbert or whether it will remain based in New York City, have yet to be worked out.

Colbert's half-hour show is believed to attract an average of 1.1 million viewers, less than half as many as those who tune into the Late Show.

When the new appointment was announced, CBS president Leslie Moonves said: "Stephen Colbert is one of the most inventive and respected forces on television.

"David Letterman's legacy and accomplishments are an incredible source of pride for all of us here, and today’s announcement speaks to our commitment of upholding what he established for CBS in late night."